1. Field of the Invention
This invention relates generally to an apparatus for transmitting torque to the sun gear of a planetary gear unit during a freeness check using a drive hub having ball plunger.
2. Description of the Prior Art
A planetary gear unit of an automatic transmission for an automotive vehicle includes a sun gear formed with a series of splines, a ring gear, and a planet pinion carrier supporting planet pinions, which continually mesh with the ring gear and sun gear.
Each planet pinion carrier assembly is tested after assembly for freeness, i.e., the ability to rotate without frictional restraint due to contact with other components. This testing requires rotating the gears and pinions of the planetary gear unit by rotatably driving the sun gear with a drive hub.
Conventionally the drive hub experiences significant wear on the front edges of splines as it makes initial engagement into the splines of the sun gear.
It is not uncommon for the drive hub to require replacement after 35,000-40,000 cycles at a high replacement cost, requiring an hour or more of maintenance labor and production downtime.
Additionally, the machine performing the test experiences intermittent stoppages (approximately 5% of cycles) due to the drive hub not meshing consistently with the sun gear, thus creating significant losses in productivity.